Normal Behavior
by A Deed Without a Name
Summary: Sam performs research on angels. Specifically, Castiel. Crackfic. WARNING: Contains hints of Destiel and Wincest.


**The last few things I posted have been angsty as hell. So I wrote something unbelievably stupid to make up for it.**

 **Note: This isn't based off of canon...as far as we've seen, Castiel really doesn't exhibit all that much avian behavior. And what little he does (head tilts, arms held slightly out to his sides like wings) is probably more Misha's acting style than his character. This is just a crackfic. Because bird!angels and purring!angels are both kinklets of mine.**

* * *

Castiel's bed had almost completely disappeared - only the bottom left corner, the old spring mattress bare, was still visible. Everything else had been swallowed by a soft, warm avalanche of fabric. Normal items, like blankets and pillows, and weirder ones, too. A white flag with the symbol of the Men of Letters printed on it in black. A trench coat. A pair of jeans that looked suspiciously like Dean's favorite pair. A flannel button down that was definitely Sam's.

Sam cleared his throat.

"Well," he said. "That explains who's been raiding the dryer."

"Yeah. I told you it wasn't me," Dean agreed, sounding a little smug. He was standing right next to Sam in the doorway to Castiel's room, so Sam had to lean out of the way when he folded his arms and then glanced at him. "So...d'you get why I wanted you to come and look at this?"

"Yeah," Sam agreed, assessing the mountain of clothes and bedding with an eye trained by thousands of hours of researching and gathering clues. Actually, it was shaped more like a volcano than a mountain, he supposed: there was a deep bowl in the center instead of a peak. "Cas built a nest."

"Which is weird as hell," Dean prompted. "Right?"

"Well, it's..." Sam hesitated, thinking. He remembered Castiel doing a ton of weird stuff, but not nesting. "No, he's never done this before."

"Reckon he's cursed?" Dean asked. From his tone, Sam could tell that he didn't. He was taking a stab in the dark because he didn't have any ideas.

"No," Sam said, shaking his head. "I'm...not even sure angels can be cursed. Even ones as beat up as Cas is."

"Then what's going on?" Dean demanded. Like Sam would really have the answer.

"How the hell should I know?" he shot back. "You're way closer to him than I am. He's been following you around like a lost puppy lately."

"Or a homing pigeon," Dean muttered. "Can't go anywhere without him sniffing me out. I'm surprised he wasn't with me when I found...that." He flapped a hand towards the nest. "Why's it full of our clothes, anyway?"

"I don't know, but it's kinda creepy, isn't it?" Without any warning whatsoever, something clicked for Sam. He blinked and looked at Dean. "Wait a minute. What'd you just say?"

"I asked you why Cas has apparently been sleeping in our underwear," Dean replied, clearly bothered by that fact. Sam shook his head again.

"No, no, I meant before that," he said.

"When I...called him a pigeon?" Dean asked uncertainly, frowning.

 _"Yes."_ Sam spun around and started down the hallway. About a second later, he heard Dean follow him. "Let's go find Cas. I think I might know what's up with him."

"Aw, c'mon," Dean complained, jogging to catch up with Sam. He had a definite advantage over his bow-legged older brother, a realization that never failed to make him feel vaguely superior. " _Find_ him? Seriously? I barely got rid of him, and trust me, it took just about forever."

"Where'd you leave him?" Sam asked, glancing at Dean, walking beside him. "I've got a theory, and I need to talk to him to know if I'm right or not."

Predictably, Dean scowled. "I ever told you how much I hate your 'scientific curiosity'?"

Sam shot him a grin, amused at how easy it was to get under his skin. "Yep. During our last case. When I wanted to know why, exactly, dead man's blood paralyzes vampires."

"Oh. Right." Dean grimaced, then paused. "Y'know, for something that literally everyone thought was extinct, we sure do run into a lot of vampires."

"Where's Cas?" Sam prompted, even though Dean did have a point.

Dean sighed through his nose, before reluctantly admitting, "Storage room. The big one, a couple floors down."

Sam could understand why Dean had chosen to lose Castiel in there. That particular store room (which contained the shelf that hid their dungeon) was a maze. Sam didn't actually know how big it was, never having formally mapped out its dimensions, but just from the way it felt when he was in it, he suspected that spells had been cast on it to make it bigger than the space would normally allow. Which probably shouldn't give him the creeps, but did anyway. The lighting was poor, and faulty wiring made the filthy bulbs flicker way too often. The shelves were arranged in a way that almost seemed malicious, which contributed to Sam's feeling of unease, and the organization of their contents could only have made sense to the person who did it. Weapons, ammunition, both full and empty hex boxes, canned goods, mildewing files, crates of old photographs, textbooks from the 1800s, fleshy, unidentifiable things floating in jars of formaldehyde, broken toys...there was no rhyme or reason. And they found Castiel wandering aimlessly through it all.

It was hard, since Sam only knew the room well enough to get to the dungeon and Dean wasn't much better off. But once they got close enough to Castiel to hear him bumping into things and huffing irritably, it got easier.

Sam stopped when they were a few aisles away from Castiel and shot a quizzical look at Dean, frowning. Castiel was a far cry from the ultra-powerful, winged being of light he'd been when they first met him, but he was still an angel. He should have good enough reflexes not to be knocking everything over, even in the dim light. Dean rolled his eyes and mouthed, "Looking for me." Sam understood: he was distracted. Considering how much he seemed to enjoy being around Dean and, to a much lesser extent, Sam himself, Castiel was probably _really_ distracted.

They walked up to the mouth of the short, narrow aisle that Castiel was in, and found him peering through a space he'd made on one of the shelves, frowning and chewing on his lower lip. When he heard the scuffing of boots, he glanced over at Sam and Dean with a jerky movement of his head. Immediately, his face broke into a dazzling smile. He stepped away from the shelves and - Sam noticed - puffed his chest out.

"Dean," Castiel greeted in his gravelly voice, clearly relieved. "I couldn't find you."

Sam glanced at Dean, who grimaced a little. "Yeah. Sorry about that, Cas." He made eye contact with Sam. "But listen. Sam wants to talk to you about something...I guess."

Recognizing his cue, Sam stuffed his hands into the pockets of his jeans and cleared his throat. "Cas, are you a bird?"

"What?" Castiel asked blankly, cocking his head to the side with a frown. He seemed to get what he'd heard before Sam could repeat it. "No. Of course not. I'm an angel." He rolled his shoulders self-consciously. Or maybe he was just trying to get his trench coat to fall better. "Just because I have wings doesn't mean I'm a bird...and, actually, I don't even have wings at the moment. I thought I'd told you two this before."

"Uh...'at the moment'?" Dean repeated, confused. Sam, who had wanted to clarify his question before Dean started talking, suppressed a sigh.

"They'll grow back," Castiel replied matter-of-factly. "Eventually. Probably not in your lifetime, which is a shame, because I would've liked you to - "

"All right, you're not a bird," Sam interrupted. This thing about Castiel's wings growing back actually sounded pretty interesting, but it wasn't what Sam wanted to grill him on right now. "Sorry. That wasn't what I meant - it came out wrong. I guess...are birds _based_ on angels? Like, are you guys similar?"

"No," Castiel said flatly.

Undeterred, Sam continued. He was very used to interrogating unwilling subjects. Demons, crooked cops, Dean. "See, the only reason I ask is 'cause you've been doing a lot of...uh... _birdy_ things. Especially recently."

All of Castiel's happiness at seeing them (mostly Dean) was gone now. He folded his arms over his chest, almost defensively. "Like what?"

"Well...the nesting, to begin with," Sam said, glancing at Dean for backup. Dean nodded.

"The nesting?"

"The pile of our clothes that you've got in your room," Dean clarified, almost-but-not-quite glaring at Castiel. "The room we gave you 'cause you need to sleep now, since your flame's burning so low. So I'm gonna assume you've been spending your nights in that thing."

At Dean's thinly-veiled accusation, Castiel did something that Sam had never seen him do before, something he hadn't even known he _could_ do: he blushed.

"You went in my ne - room?" he demanded, indignant. "That is a breach of trust."

"Okay, one, we didn't touch your creepy nest," Dean countered. "The door was just open, and we looked in. And two, you stole, like, half our boxers. That is _way_ more of a breach of trust." Dean eyed Sam as, in a low mutter, he added, "Not that I'm not used to it. Since someone's had a _pathological_ need to steal my shit since he was about six."

Now Sam was sure _he_ was blushing. "Not your _underwear_!" he exclaimed. Just blankets and jackets and cologne. Things that smelled like his older brother...and his borrowing of them certainly didn't ramp up when Dean was gone for more than a day.

Castiel gave Sam a look he couldn't decipher before defending himself with, "Lots of things make nests. And it's fairly rare for my kind, unlike birds." Almost as an afterthought, he added, "But please stay away from mine."

Sam made a mark on his mental notepad: _Territorial_.

"The nesting isn't the only thing," he said out loud. "There's your thing with mirrors, too."

"What thing with mirrors?" Castiel asked testily.

"Oh, hey, yeah," Dean realized. "I'd forgotten about that. You still owe me for one of Baby's side mirrors, by the way. I had to replace the whole damn thing."

Castiel, uncomfortable, said, "I don't recall that."

"You put an angel blade through it," Sam stated. "And through about a dozen others, too. You fight with mirrors. Like a bird."

"No, I don't!" Castiel snapped, unfolding his arms. "You don't understand. I can see Grace, and that's how I identify other angels. The first thing I see in a mirror is my Grace, and with how hostile my brothers have been towards us lately - "

"You don't recognize it as _your_ Grace?" Sam interrupted, raising a brow. Castiel averted his eyes.

"Not...not right away," he admitted quietly.

"Well. Okay." Dean cleared his throat, glancing down at his boots and then back up. "As long as we're on the subject of problems you've got with things made outta glass...sliding doors."

"What about them?" Castiel asked. His expression, though, betrayed the fact that he had at least an idea as to what Dean was talking about.

"A few months ago, me and you worked a case together," Dean began. He looked at Sam. "You were...I don't remember. Rereading _The Lord of the Rings_ or something." Sam frowned, miffed. "Whatever. You didn't come with us, that's the point. But we visited this house that somebody had sacked, and I let Cas out through the sliding glass door so he could check the back yard, and he couldn't get back in."

"It was locked," Castiel, exasperated, told Sam.

"Uh, no." Dean shook his head, smirking a little. "It wasn't. You'd _seen_ me open it, and you _still_ ran into it. A few times, going by that nice face-print you left on the glass. And I was upstairs, so I didn't know what was going on until you started freaking out."

"'Freaking out'?" Sam asked, while Castiel sighed and rolled his eyes.

"Banging on the door," Dean explained. "Yelling my name. Uh... _squawking_." Remembering something, he laughed a little. "And don't even get me started on this other case - god, that one was _years_ ago. I had to drag him away from a bird feeder."

"That never happened," Castiel protested, angrily puffing himself up. But Sam, fascinated, had largely stopped paying attention to him.

"He was eating birdseed?" Sam asked incredulously. "Seriously?"

"Ohhh, yeah," Dean confirmed, nodding and grinning, obviously enjoying himself. "Only after he polished off the suet cake, though. And, man, you shoulda seen the way he was defending that thing from all the chickadees. And _me_ , too. Screeching and flapping that trench coat all over the place - "

 _"Dean!"_ Castiel interrupted him with a...well, a screech. "This isn't funny at all. _Please_ stop exaggerating about me - none of that's true."

Sam glanced at him, then blinked, shocked. Dean had basically the same reaction. Castiel had settled himself into one weird position: feet spread wide, head lowered, shoulders squared, arms held far out to his sides so his coat fell open. And made him look bigger. His blue eyes were narrowed with anger and hurt.

"Uh...what the hell's he doing?" Dean asked slowly, glancing at Sam. Sam wasn't sure when he'd become the expert on their live-in seraph, but he answered anyway. _Agressive._

"Threat display," he replied. "Birds of prey do it all the time."

Upon hearing that, Castiel hastily shook himself out of the position. He straightened up, dropped his arms, and pulled his feet back together - his aggression was still obvious, though, in the way that he was glaring at Dean. It wasn't long before he turned that glare on Sam, who swallowed self-consciously.

"So, Sam," Castiel said, voice heavy with sarcasm. "Have you noticed any _other_ avian habits of mine?"

"Yeah, actually," Sam admitted, glancing discreetly at his older brother, who he knew wasn't going to be happy about this one. "I think you've imprinted on Dean."

"That's ridiculous," Castiel declared instantly, his sapphire glare sharpening. "Angels definitely don't imprint."

"Wait a minute," Dean said, raising a hand and ignoring Castiel as he shot a look at Sam. "If he's imprinted on me, then does that mean I'm like his...mom or something? 'Cause that's..." He went through a full-body shudder that was a better descriptor than any word he could have come up with.

"Nooot exactly," Sam replied, drawing the first word out as two pairs of pale eyes bored into him.

"So what's it mean?" Dean wanted to know.

"What on Earth would make you think I've 'imprinted' on your brother?" Castiel asked. Sam could hear the quotations around "imprinted."

Sam decided it would just be easier to answer both questions at the same time. Without saying a word, he stepped between Dean and Castiel. His size meant that his older brother was completely blocked from the angel's gaze. So, just as Sam had expected, Castiel moved. Ninety degrees to Sam's left, to be precise, so that he could see Dean again. The smoothness of the instantaneous movement made him suspect it was reflexive. Castiel hadn't even thought about it.

"That," Sam said to both Dean and Castiel, gesturing to the angel.

"This doesn't prove anything," Castiel said stubbornly at the same time that Dean admitted, "I still don't get it." Somehow, Sam managed to pick out both statements, and they resigned him to the fact that he needed to do another demonstration.

Sam locked eyes with Castiel and, making sure he was watching him, slowly stepped back, so he was standing next to Dean again. Then he put a hand on the denim-covered curve of his tight ass, making Dean twitch with surprise and definitely not fulfilling a guilty desire he himself had harbored since middle school.

 _"Mine!"_ If the store room hadn't been as impossibly big as it was, Castiel's enraged screech probably would have ruptured Sam's eardrums. As it was, he heard several glass jars shatter violently nearby. The thought of cleaning up their contents filled him with a queasy dread - or it would have, if he hadn't been preoccupied with the angel blade that Castiel had pressed up against his throat. If he swallowed, it would slice into him, he realized...which, of course, made his mouth flood uncomfortably with saliva.

"Were you thrown out of your nest?" Castiel growled, making an aggressive chirring sound in the back of his throat. He'd leaped for Sam, shoving him up against a set of shelves with so much force that it was a miracle it hadn't tipped over. Sam could feel aching bruises cropping up all over his back. Castiel was keeping him in place with one hand and using the other to hold his sword against his throat, glaring at him with raw hate. Dean was standing off to the side, stunned. "Laying a hand on him without any kind of display - like he'd choose _you_ , anyway. Your plumage is _pathetic_ , especially for a tercel of your size." He cast a withering glance towards what Sam realized (not without some offense) must be his hair.

"Oh, shit," Dean blurted suddenly, getting over his stupefaction. He looked equal parts afraid for Sam and disturbed by the realization that Castiel wanted to raise a flock of fledglings with him - which must have just dawned on him. "What do I do?"

"Uhhh - I don't know." Sam frantically cycled through everything he knew about birds. It wasn't a whole hell of a lot, actually. After a few precious seconds, during which Castiel spat chirps and clucks at him that he couldn't hope to understand, Sam remembered visiting a pet store once during the course of an investigation. What the owner had done to calm a nervous parrot. "Try scratching under his chin!"

Dean did, albeit reluctantly. Sam understood that. Castiel had his blade handy, he was pretty tense right now, and he might reason that Dean could probably still lay eggs with a hand missing. Or...maybe Castiel thought he'd be the one laying the eggs. Maybe eggs weren't involved at all. Sam seemed to know even less about angels than he did birds.

Useless speculations about angel eggs aside, Castiel didn't cut Dean's hand off when he reached under his jaw and started scratching at the soft flesh there with blunt fingernails. Quite the opposite, actually. He relaxed almost as soon as Dean touched him, the tension melting out of his muscles. Both of his hands dropped away from Sam, who took the opportunity to swallow several times, and the angel blade slipped out of his lax fingers and clattered loudly against the cracked cement of the floor. Castiel didn't even seem to register the sound. He was leaning heavily into Dean's scratching, an expression of perfect bliss plastered across his face and his pupils dilated so far that only the thinnest ring of blue was visible around them. As Sam watched, Castiel's eyes slid closed, and a contented, gravelly rumble rose up out of somewhere deep in his chest. It took him a few seconds of listening to it to realize that the angel was purring.

Dean glanced at him, utterly bewildered. "Sam." He looked back at Castiel, whose purring was steadily growing louder. "Just, uh...what does this mean, exactly?"

Sam crossed his arms and sighed, frustrated.

"It means I need a new hypothesis."


End file.
